1. Fields of Invention
The present invention relates to hydraulic winching systems for hydraulic backhoes and the like, and more particularly to a conversion system for such vehicles, which with the conversion of the present invention use a boom and winch line sub-system that allows the "backhoe" to be used in operations such as draglines, lift cranes, clamshell diggers or loaders, pile drivers, etc.; and even more particularly to such a system in which "true free fall" is achieved on a repetitive, regular, operating basis, when the load and/or work implement being carried by the boom is allowed to freely descend under the force of gravity. The present invention also relates to the providing of a combined boom/winch system as an accessory piece of equipment for backhoe vehicles and the like, to convert them into a crane type piece of equipment. Additionally, the present invention relates to an improved hydraulic winch system for cranes and the like which achieves "true free fall" for the load, when desired, on an ongoing, regular operational basis with the use of an hydraulic motor directly driving the winch drum and a supplemental braking system for the winch drum, such as for example a disc brake.
2. Prior Art & General Background
A backhoe type vehicle is well known in the art as a very versatile piece of equipment. Although originally used as an excavator, "backhoes" are also usable alternatively, with the proper accessory equipment, as for example a scrap metal/grapple, a logging-heeler, a logging-grapple, scrap shearer, an hydraulic tree feller buncher, etc. Such backhoes typically have a boom pivotally supported underneath by an angled hydraulic cylinder, with the boom carrying a front, accessory arm, which is pivoted about an upper axis by a top hydraulic cylinder to be moved toward and away from the cab under the operator's control; hence the term "backhoe." Winches generally have not been used on backhoes, and as a general rule backhoes heretofore have not been usable as a crane type piece of equipment.
However, as a separate piece of equipment of a different type, cranes have been well known which can be alternatively configured to be a dragline, a lift crane, a clamshell digger or loader, a pile driver, etc., by appropriately changing the accessory equipment attached to the boom of the crane. Typically, such cranes use a lattice type boom made of lacings and cords, forming an open structure, and use winches usually powered by hydraulic motors of the gearing type, with the hoist winch and the in-haul winch mounted on a common shaft on the main body of the crane. Alternatively, expandable clutches working on the cylindrical interior of a drum are typically used to transmit the power from the main power or prime mover. In either case, for braking of the winch drum, externally contracting band brakes working against the exterior, cylindrical surface of a drum have been typically used to brake the winch.
Thus, in the prior art, to do the jobs the backhoe does best and do the jobs a crane was designed to do, it has been practically necessary to have separately both a backhoe and a crane, resulting in very great expense for the user, with duplication of the crawler (or wheeled) and cab/prime-mover portions of the two pieces of equipment. This very unsatisfactory situation has been with the heavy equipment industry for a long period of time.
The present invention, it is believed, is the first to achieve on a practical, reliable, cost effective, quick-change-over basis, a combined backhoe/crane system embodied in a single piece of main equipment, with the change over from backhoe to crane being achieved with an accessory system, thereby avoiding any substantial duplication of the main equipment, with the equipment achieving "true free fall" for the load when desired on an ongoing, operational basis.
There apparently has been at least one attempt at combining backhoe and crane systems on a combined "backhoe," as indicated by a brochure on the HITACHI MA125U STV amphibious soft terrain vehicle apparently printed in 1982. However, it mounts its two winches side-by-side on the main body of the backhoe and does not mount the hoist winch on the boom itself in the line-of-sight of the operator, as in the preferred embodiments of the invention. Additionally, it apparently uses relatively low torque hydraulic motors for the winches.
Thus, additionally, one of the problems that has persisted in the prior art over a long period of time with hydraulic crane systems, is one of using hydraulic gearing motors, has been the lack of "true free fall" of the object being carried from the end of the boom by the cable line, when the hydraulic winch lets loose on the hoist line. Thus, usually because of the retarding or dragging action of the hydraulic winch gearing elements, the object being carried by the cable line is slowed down in its descent under the force of gravity.
Typically, hydraulic winches of the hydraulic gear type have a relatively low torque, for example 200 foot/pounds, requiring that they be torqued up to drive a winch for the loads encountered in cranes. Such reduction gearing usually involves a ratio of the order of 20:1 and uses planetary gearing, including for example input sun gear, secondary sun gear, primary planet gear, secondary planet gear, ring gear, output planet gear, etc.; note for example the PD15 hydraulic winch manufactured by Braden Winch Co. of Broken Arrow, Okla., which is used on hydraulic cranes for hoist lines and the like. When the hydraulic motor is cut off to allow the hoist cable to "freely" spool out, the reduction, planetary gearing still is being rotated, producing significant retardation or drag on the line.
Although some manufacturers claim "free fall" characteristics for its released hoist line, when the hydraulic gear motor has been cut off, such has been meant in the prior art only as a relative term, and it is believed that "true free fall," which allows the load or work implement at the end of the cable to freely move under the force of gravity without any significant retardation or drag, has not been achieved in such a system on a regular, operational, repetitive basis until the present invention.
As an indicator of the difference in the "free fall" characteristics of the prior art hydraulic gear motor compared to that used in the exemplary preferred embodiment of the present invention, the former takes of the order of a 1,500 lb. minimum load to initiate spooling out of the hoist line in "free fall," while the present invention in the initial prototype required only approximately 150 lb. minimum load.
Additionally, it should be understood that the so-called "emergency" subsystem, which is provided in some prior art hydraulic cranes as a safety factor, which allows a load to be quickly dropped to prevent for example tip over of the crane due to imbalance, is just that, namely a one-time-usage, emergency system, analogous to the safety "seat ejector" in an airplane. In one such "emergency" system, a pin connecting the reduction gearing to the drum is pulled, allowing the drum to then to "truly" freely rotate without the supplemental gearing. However, if the motor is attempted to be "re-engaged" before the pin is properly reassembled, the motor train can be substantially damaged. Additionally, the operator loses all control over the hoist line and its load, once the "emergency" button is actuated.
In contrast, the present invention achieves "true free fall" on a repetitive, regular operational basis, every time it is desired to have the load or working implement suspended from the cable off of the boom to freely fall or drop under the force of gravity. Such action allows, not only emergency use, but repetitive use to speed up the operation at hand on a regular operational basis, since no unnecessary time is lost due to delayed load or implement movement.
In the preferred embodiments the invention achieves these long desired, advantageous goals by utilizing a high torque hydraulic motor directly driving the winch drum, that is without any supplemental, interconnecting gearing, and a supplemental braking system, preferably a disc brake system. Although there have been prior attempts to combine an hydraulic, high torque motor to directly drive winches (see Hagglunds' Viking Motors for very large crane winches and the like, and the "HYDROSTAR" MRH 95 & 2/3-95 apparently used on a trawl winch), none it is believed were part of a backhoe-to-crane conversion system, but rather a regular crane or trawl winch installation, and additionally used, to the extent known, the standard, old type of externally contracting band brake, in comparison to the disc type brake of the preferred embodiment.
Thus, in summary, the present invention allows a backhoe to be quickly and easily converted to a crane type piece of equipment, with preferably at least part of the winching system being included on the boom itself, and with the winching system being capable of "true free fall" by preferably using a high torque hydraulic motor directly driving the drum winch with a supplemental brake system being provided, preferably of the disc brake type. Such an achievement allows the converted crane "backhoe" type vehicle adapted with the present invention to operate much more quickly and safely, in comparison to those of the prior art, without having any substantial duplication of heavy, expensive equipment.